Help? Family trouble. More details below...?

My parents are getting a divorce. I can't even explain how I feel about this. Our family (me, my dad, my mom, and my little brother) is very close. And then suddenly they want to split up and I dont know why. I'm 15 and my brother is 12. I don't know why but I'm taking it a lot harder than he is. He actually got excited when my mom talked about the house she wants to buy. I have a lot of friends but I feel like I'm whining too much if i talk to them about it. I've never felt so alone, I feel like I can't talk to anyone. We haven't sold the house yet but my moms always gone now. She also has a boyfriend, don't ask how I know this. When she's at home she's always locked up in her room and i feel like i cant talk to her. My dad and i are very close but he's really depressed about this whole thing cause it was my moms idea to get the divorce. So that makes me feel like Id be making it worse if i talked to him about it. I also am basically taking responsibility of everything. My dad's working all the time and my moms basically out partying all the time so I'm taking care of my brother too. I clean and cook for the both of us, along with trying to survive 10th grade. We're also really tight on money and its so stressful I want to scream. And I feel awful about whining about it because other people have worse things going on. But I can't help it. I've tried everything. I don't want to sound like a drama queen but sometimes I wish i could just die. I'm tired in everyway possible, physically, mentally, emotionally. I want to lie down and sleep for a million years but I never have time. Im just plain exhausted. And typing this all out on Yahoo makes me feel even more pathetic but I have to get it out. Thanks for reading this really long and melodramatic thing. If you have advice, I'll take it.